Automate Docker deployment with Gitlab

# Setup 2 steps:
#   dockerize Build container
#   deploy    Deploy to remote server
stages:
  - dockerize
  - deploy
  
dockerize:
  stage: dockerize
  image: docker
  # Run this step only when code is pushed into master branch.
  # Might want to make it "tags" to dockerize only releases
  only:
    - master
  # Use Docker in Docker service, to build Docker in Docker
  services:
    - docker:dind
  script:
    # Login to Gitlab Docker registry using built-in [variables](https://docs.gitlab.com/ee/ci/variables/)
    - docker login
      -u "$CI_REGISTRY_USER"
      -p "$CI_REGISTRY_PASSWORD"
      $CI_REGISTRY
    # Build it! Name will be project_name:branch_name
    - docker build --pull -t $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG .
    # Push freshly built image to Gitlab registry
    - docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG

deploy:
  stage: deploy
  # Use this as base image to get small SSH container
  image: instrumentisto/rsync-ssh
  only:
    - master
  script:
    # Add key, it needs to be set up as pipeline variable
    - eval $(ssh-agent -s)
    - echo "$DEPLOYER_KEY" | tr -d '\r' | ssh-add - > /dev/null
    - mkdir -p ~/.ssh
    - chmod 700 ~/.ssh
    # Remove known hosts check
    - echo -e "Host *\n\tStrictHostKeyChecking no\n\n" > ~/.ssh/config
    # Explained down below
    - ssh -t [email protected] "docker login -u "$CI_DEPLOY_USER" -p "$CI_DEPLOY_PASSWORD" $CI_REGISTRY &&
      docker pull $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG &&
      docker stop example-name; docker rm example-name;
      docker run -d -p 31227:80 --name example-name $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG"

# SSH into server, run last argument as command and disconnect
ssh -t [email protected] ""

# From remote server login into Gitlab registry
# [how to get and setup deploy tokens](https://docs.gitlab.com/ee/user/project/deploy_tokens/#gitlab-deploy-token)
"docker login -u "$CI_DEPLOY_USER" -p "$CI_DEPLOY_PASSWORD" $CI_REGISTRY"

# Pull new Docker image
docker pull $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG &&

# Stop and remove existing container, use ";" instead of &&
# since server does not have this container when deploying first time
docker stop example-name; docker rm example-name;

# Start container in background, expose port 80 to 31227 and name it
docker run -d -p 31227:80 --name example-name $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG"

server {
    server_name example.com;

    location ~ / {
        # Add headers, so application knows it is behind proxy
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $remote_addr;
        # Proxy to container. Port must be same as in deploy script
        proxy_pass http://127.0.0.1:31227;
    }
}